The power limit of a gas turbine is the power at which a gas turbine can be operated at a maximum, and is determined by the mechanical integrity of the individual components of the gas turbine. The component which first reaches the limit of its mechanical load-bearing ability is decisive for the power limit of the gas turbine. Typically, these components are the downstream turbine blades in the main flow direction which, because of their radius and the greater centrifugal forces associated therewith and acting on the turbine blades, are most highly loaded.
In order to achieve the highest possible energy yield from the gas turbine, it is operated as close as possible to the power limit. The instantaneous power of the gas turbine is usually determined indirectly at the electrical outputs from an electric generator driven by the gas turbine in the gas turbine plant, by measuring the currents, voltages and possibly phase angles, since it is assumed that the instantaneous output power from the electric generator depends directly on the instantaneous power.
The instantaneous power of the gas turbine can briefly reach or exceed the power limit defined for the gas turbine on account of fluctuations in operating parameters. In this case, the gas turbine is throttled in order to ensure its mechanical integrity.
Furthermore, it is also known, for example from U.S. 2013/227954 A1 or U.S. Pat. No. 6,718,771 B 1, that the power limit value can be determined variably, depending on the ambient temperature, wherein the power limit value rises with falling temperatures. However, the problem with such a dependence is that the power limit adaptation for changing ambient conditions can be determined only in a restrictive manner.